7j43kThe minimum radius for a Great Northern N-2 (2-8-8-0) was 522'. For an N-3, it was 359'.
There are a couple of GN enthusiasts in these forums who I suspect can discuss the rather spectacular N-3s in detail, including whether their fancy nickel-steel boilers suffered the way many contemporary design efforts did.
Overmod 7j43k The minimum radius for a Great Northern N-2 (2-8-8-0) was 522'. For an N-3, it was 359'. This was far from a 'nominal' rebuilding -- among the changes was installation of cast-steel beds with driving-axle roller bearings. As I think one of the very logical consequences of this would be lateral-motion device installation, I suspect the reason for the indicated difference would be substantially associated...
7j43k The minimum radius for a Great Northern N-2 (2-8-8-0) was 522'. For an N-3, it was 359'.
This was far from a 'nominal' rebuilding -- among the changes was installation of cast-steel beds with driving-axle roller bearings. As I think one of the very logical consequences of this would be lateral-motion device installation, I suspect the reason for the indicated difference would be substantially associated...
nominal: in name only
"far from a 'nominal' rebuilding" would then be a true rebuilding.
I think I will stay with the concept of "in name only", since the only parts reused from the N-2's were journals (non-roller bearing), axles, driving wheel centers, sandboxes, turbo generators and some lesser items.
However, the two classes were quite similar in overall dimensions. Which is why I found the large difference in minimum radii especially interesting.
There may or may not have been lateral-motion devices on the N-3's. I doubt there were on the N-2's. Don't forget that many locomotives also used the simple concept of increased clearances for axle side motion.
It's interesting that there are a couple of very different semantic meanings for the phrase 'nominal rebuild' -- and we've been using them.
To me, a 'nominal' rebuild or repair is one that's called that, but there is comparatively little actual rebuilding or repair involved... it is more a change 'in name only'. (Like the semantics in the phrase 'nominal charge')
In your version, the new structure is so completely different that to call it a 'rebuild' (as with some famous examples of diesel locomotives in the '60s) rather than a new locomotive that happens to share some parts with an older predecessor starts to look like Jason's ship or grandfather's axe if we call it 'rebuilt'. This too is true.
What I suspect is that this is tax-related, much as the Frisco 2-8-2 rebuilds of the late '40s were. It isn't the sort of rebuilding represented by the Reading 4-8-4s, where the structure of the older locomotive was substantially retained to save money, and the resulting locomotive didn't share 'historical class' or common service consideration with the older locomotive...
(Incidentally, were you ever successful in contacting a civil engineer or equivalent who had actually supervised or bossed either a passenger wye or yard-trackage job that involved transitions or easements in practice? We've heard from someone reasonably expert in industrial siding work, and from AREA/AREMA text references, but I still agree with you that it would be nice if someone who KNOWS from experience would chime in here.)
I worked in the engineering department for both the Union Pacific and Chicago and North Western railroads and designed and laid out in the field many track layouts. We never used spirals on industry, yard, or other non-main trackage; low-speed main line (10 MPH) curves didn't get spirals either. In addition, we didn't use any superelevation on those types of curves.
If track speed required it we would lay out main line curves with spirals on both ends of the curve; the rest of the curve was a normal circular curve with constant radius (unless a compound curve was needed because of topography or other obstacles).
Kurt Hayek
sandiego I worked in the engineering department for both the Union Pacific and Chicago and North Western railroads and designed and laid out in the field many track layouts. We never used spirals on industry, yard, or other non-main trackage; low-speed main line (10 MPH) curves didn't get spirals either. In addition, we didn't use any superelevation on those types of curves. If track speed required it we would lay out main line curves with spirals on both ends of the curve; the rest of the curve was a normal circular curve with constant radius (unless a compound curve was needed because of topography or other obstacles). Kurt Hayek
Kurt, thanks for the info. If I can ask, what size turnouts did you generally use in yards? and what radius curve might have been typical?
Sheldon